Contents

example_pvl_Purdue_albedo_model

Example calculation of ground reflected diffuse irradiance on the rear surface of a PV module.

clc
clearvars
close all

Load weather data

TMYData = pvl_readtmy3('723650TY.csv');
TimeMatlab = TMYData.DateNumber;
dv = datevec(TimeMatlab);

tfilter = and(dv(:,2) == 8, dv(:,3) == 2); % Select August 2

Time = pvl_maketimestruct(TimeMatlab(tfilter), ones(size(TimeMatlab(tfilter)))*TMYData.SiteTimeZone);

Sun position calculations

HExtra = pvl_extraradiation(pvl_date2doy(Time.year,Time.month,Time.day));
Location = pvl_makelocationstruct(TMYData.SiteLatitude,TMYData.SiteLongitude,TMYData.SiteElevation);
PresPa = TMYData.Pressure(tfilter)*100; %Convert pressure from mbar to Pa
[SunAz, SunEl, AppSunEl, SolarTime] = pvl_ephemeris(Time,Location,PresPa,TMYData.DryBulb(tfilter));
SunZen = 90 - AppSunEl;
AM = pvl_relativeairmass(SunZen);
AM(isnan(AM)) = 20;

Describe system

SurfTilt_Front = 30;
SurfTilt_Rear = 180 - SurfTilt_Front;
SurfAz_Front = 180;
SurfAz_Rear = 180 + SurfAz_Front;
Albedo = 0.25; % 25% albedo coefficient for concrete/vegetation

EtoH = [1 0]; % Elevated (EtoH = 1) and ground-mounted (EtoH = 0)

Run calculation

for i = 1:length(EtoH)

    I_Alb_Front(:,i) = pvl_Purdue_albedo_model(SurfTilt_Front, SurfAz_Front, EtoH(i), Albedo, ...
        TMYData.DHI(tfilter), TMYData.DNI(tfilter), HExtra, SunZen, SunAz, AM);
    I_Alb_Rear(:,i) = pvl_Purdue_albedo_model(SurfTilt_Rear, SurfAz_Rear, EtoH(i), Albedo, ...
        TMYData.DHI(tfilter), TMYData.DNI(tfilter), HExtra, SunZen, SunAz, AM);
end

Plot the results

figure
hold all
s = {'r-','b-','ro','bo'};
for i=1:length(EtoH);
    plot(Time.hour, I_Alb_Rear(:,i), s{2*i})
    plot(Time.hour, I_Alb_Front(:,i), s{2*i-1})
end

xlim([-5 22])
xlabel('Hour of Day')
ylabel('Albedo Irradiance (W/m^2)')
legend('Rear (elevated)', 'Front (elevated)', 'Rear (Ground Mounted)', 'Front (Ground Mounted)', ...
    'Location', 'NorthWest')
title({'Albedo Irradiance on a Bifacial Module';'Albuquerque - Aug 2'},'FontSize',14)

Copyright 2018 Sandia National Laboratories

Published with MATLAB® R2018a